Technical changes in the machine tool industry have facilitated automatic machining of parts, as by the use of numerically controlled machines, flexible machining centers, and the like, and the use of robots for loading and unloading parts to and from machine tools.
Typically, a workpiece is held in a rotary workholder, such as a jaw chuck, in which work gripping jaws (so-called "top jaws") are often preformed to the contour of the surface of the part to be gripped. The parts can be automatically fed to the work gripping jaws, but where the part is changed so that the portion gripped is of a different size or shape than before, new top jaws are required. These are usually machined to the desired shape and size, often on the machine tool itself. Machining the top jaws or changing the jaws are both time consuming and neither operation lends itself to automation. For example, even the changing of work gripping or so-called "top jaws" carried on master jaw slides of a chuck requires the removal of several fasteners, the proper locating of the top jaw and then securing the jaw in place. Often the work gripping surface of this jaw is then machined to conform to a workpiece.
From the above it will be apparent that a need exists to permit converting a workholder adapted to grip a part of given size and dimension to a configuration in which a part of different size and/or configuration can be gripped without changing the chuck on the machine tool, which requires disconnection of power actuators, interconnections, and the like, and without the time consuming operations of removing threaded fasteners and adjusting top jaws, which preclude automation. It will be appreciated that changes of a chuck or changes of a top jaw are complex in that they involve multiple steps and some adjustments that require sensing and feedback, which under the present state of the art, requires human operator intervention and is beyond the ability of robot operation.